Polishing pad for use in chemical/mechanical planarization of semiconductor wafers having a transparent window for end-point determination and method of making

ABSTRACT

A porous polishing pad for use chemical/mechanical planarization of semiconductor wafers is provided with a transparent section formed in a section of the porous polishing pad by direct injection of a polymeric material into a modified portion of the pad. The modified section may be either a low density area, or may be created by removing a complete vertical section of the pad. The injected polymer forms an integral window with the pad by flowing into the matrix of the pad at the pad/window interface. No additional reinforcement is required to hold the window in place; however, adhesive and/or another impervious layer may be attached behind the window for additional support. In an alternative embodiment, a separate and distinct window-plug is inserted into a cutout section of the pad, and bonded to the pad by one or more binding film layers on the back, non-working surface of the pad.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] Priority of provisional application No. 60/365,100 filed on Mar.18, 2002 is herewith claimed. The present application is, also, acontinuation-in-part of U.S. patent application Ser. No. 10/349,201,filed on Jan. 22, 2003.

BACKGROUND OF INVENTION

[0002] The present invention is related to polishing of materials, inparticular to the chemical mechanical polishing (CMP) of integratedcircuits. Specifically, a method for placing a transparent section in apolishing pad is described. In particular, the present invention isdirected to forming or placing an end-point-detecting, laser-transparentwindow in a CMP polishing pad disclosed in above-mentioned parentapplication Ser. No. 10/349,201, or the porous polishing pad disclosedin commonly-owned U.S. patent application Ser. No. 10/087,223, filed onMar. 1, 2002, which applications are incorporated by reference herein.The CMP porous polishing pads disclosed therein are made of a matrix ofporous paper-making fibers that is impregnated and bound together with athermoset resin. Such a polishing pad is a matrix of absorbent cellulosefibers, for example, and are impregnated with a thermoset resin,preferably phenolic, is densified, and cured to provide a rigid, yetporous structure. The porous CMP polishing pads thereof are made by awet-laid, specialty paper-making process.

[0003] In the field of semiconductor manufacture, numerous integratedcircuits are produced on wafers through layers of wiring devices. Duringthe process of forming layers and structures, the topography of thesurface becomes increasingly irregular. The prevailing technology forplanarizing the surface is chemical mechanical polishing (CMP). Ineffect, this process polishes the top layer of an integrated circuitprior to the depositing of another layer.

[0004] In most chemical-mechanical polishing, the working layer of anintegrated circuit is exposed to a moving polishing pad and a chemicalslurry solution. In some systems, the polishing pad, mounted on aplaten, rotates about a fixed axis, while the wafer rotates and movesacross the pad. Since material on the active layer is removed during theprocess, it is critical that the polishing process be terminated at thecorrect time. In order to control the end point of the polishingprocess, various methods have been developed. The most prevalent methodhas utilized laser interferometry which detects the end point of thepolishing process, an example of which is disclosed in U.S. Pat. No.6,280,289.—Wiswesser, et al. In these systems, a laser is mounted in theplaten and directed through the pad onto the surface of the wafer. Acontrol system detects changes in the reflected signal to determine theend point.

[0005] In order for end-point detection to be carried out, the pad musthave a section that is reasonably transparent to the wavelength of thelaser being used. Most methods for producing a transparent region in thepolishing pad involve inserting a formed, transparent plug into a holein the pad. The plug is usually secured to the pad by an adhesive filmonto the back, or rear, nonworking side or surface of the polishing pad.

SUMMARY OF THE INVENTION

[0006] It is, therefore, the primary objective of the present inventionto provide an end-point-detecting, laser-transparent window in a porousCMP polishing pad, and, in particular, for providing such a window in aporous polishing pad made of a fibrous matrix of paper-making fibersmanufactured by a specialty, paper-making process and bonded by athermoset resin.

[0007] According to present invention, a porous, wet-laid-manufacturedpolishing pad made of paper-making fibers bound by a thermoset resin isformed with a local transparent section. Transparency for purposes ofthe present invention is defined as sufficient light transmission suchthat the end-point detection system is able to function. Such a localtransparent section is formed within the pad by either removing asection of the pad itself, or by creating a low density area in thepaper-making fiber matrix. In either case, the pad is fixtured, orgrasped, between two flat plates creating a mold with the local section.The local section is filled with a polymeric material that is injectedunder pressure into the region. The polymer may be a cured polymer thatis heated to permit flow, or may be an uncured polymer that is mixedprior to injection into the local portion of the porous polishing pad.In either case, the polymer is subjected to pressure to permit flow. Asthe injected material flows into the matrix of the pad, a diffusion zonearound the perimeter of the window is created, whereby the polymericmaterial bonds securely with the pad. The resulting region thereby istransparent to the laser emanating from the end-point detection system.

[0008] The types of materials suitable for the window include amorphous,semi-crystalline, crystalline or elastomeric polymers. Generally,polymers that exhibit low shrinkage and maintain clarity upon cooling,such as amorphous polymers, are the preferred choice.

[0009] A method for creating a transparent section of the invention inthe polishing pad consists of partially or completely removing a sectionof the polishing pad, or creating a low density area in the desiredregion of the pad; forming a mold in the region by placing the padbetween two flat surfaces; injecting the polymer in a liquid orsemisolid state into the region; and allowing the assembly to cooland/or cure.

[0010] In a different embodiment, a separately-formed, steppedwindow-plug is inserted into the cutout or opening formed on thepolishing pad, and retained therein by a first impervious layer, and asecond adhesive layer.

BRIEF DESCRIPTION OF THE INVENTION

[0011] The invention will be more readily understood with reference tothe accompanying drawings, wherein:

[0012]FIG. 1A is a plan view of the polishing pad forchemical-mechanical planarization of wafers of the inventionincorporating the laser-transparent window of the invention;

[0013]FIG. 1B is detailed cross-sectional view taken along line A-A ofFIG. 1A showing the local area or region at which the transparent windowof the invention is to be formed;

[0014]FIG. 2 is a side-elevational view, in cross-section, showing thefixing plates for holding the polishing pad of FIGS. 1A and 1B forinjection of a polymer into the local area or region for forming thewindow of the present invention in the polishing pad;

[0015]FIG. 3A is a longitudinal cross-sectional view of the finishedpolishing pad with window section of the present invention, which windowsection is transparent to the laser beam emanating from end-pointdetermination equipment used during chemical-mechanical planarization ofwafers;

[0016]FIG. 3B is detailed view of the polishing pad of FIG. 3B showingthe interface between the window made during the process shown in FIG. 2with the remainder of the porous polishing pad;

[0017]FIG. 4 is a cross-sectional view of a modification of thepolishing pad with transparent window section of FIGS. 3A and 3B, whichwindow section is provided with a stepped, or larger-diameter lowersection for contact against retaining platen of a chemical-mechanicalpolishing apparatus, for ensuring greater retention of the polymericwindow section;

[0018]FIG. 5 is a cross-sectional of a second embodiment of thepolishing pad with transparent window section of the invention, where,instead of a local section being cutout, an area of lower density fromthe rest of the polishing pad is used for forming the transparent windowsection; and

[0019]FIG. 6 is a cross-sectional view of a third embodiment of thepolishing pad with transparent window section of the invention, where anindependently-molded and inserted transparent window-plug is used forforming the transparent window section.

DETAILED DESCRIPTION OF THE INVENTION

[0020] Referring now to the drawings in greater detail, FIGS. 1A and 1Bshow a polishing pad 10 which has a local region or area 12 where thepad material has been removed. The preferred polishing pad that is usedin the present invention is one that is disclosed in commonly-owned U.S.patent application Ser. No. 10/087,223, filed on Mar. 1, 2002, andparent application Ser. No. 10/349,201, filed on Jan. 22, 2003, whichare incorporated by reference herein. These porous polishing pads aremade of a specialty-paper-making matrix of a porous paper-makingfiber-structure that is impregnated and bound together with a thermosetresin. Such a polishing pad is a matrix of absorbent paper-making fibersimpregnated with a thermoset resin, preferably phenolic, is densified,and cured to provide a rigid, yet porous structure, and preferably madeby a paper-making, wet-laid process. The preferred method of productionis wet laid, since this process lends itself most readily to theincorporation of various fibers, fillers and chemicals. However, it isunderstood that other processes that produce a similar porous, fibrousstructure may also be used. These processes may include dry laidprocesses, such as spun bond, melt blown, felting, carding, weaving,needlepunch and others. The preferred fiber for producing the wet laid,fibrous structure of the polishing pad used in the present invention iscellulose fiber, and, in particular, cotton linters and lyocell fibers.Other paper-making fibers that may be used are cotton, other cellulosefibers such as wood pulp, glass, linen, aramid, polyester, polymer,carbon, polyamide, rayon, polyurethane, phenolic, acrylic, wool, and anynatural or synthetic fiber or blends thereof. The polishing pad used inthe present may incorporate nanometer-sized abrasive particles, asdisclosed in parent application Ser. No. 10/349,201, or may be apolishing pad without such nanometer-sized abrasive particles asdisclosed in above-mentioned application Ser. No. 10/087,223. It is, ofcourse, to be understood that the present invention may also be usedwith other polishing pads formed of a porous matrix-structure.

[0021] In order to form a window that is transparent to the laser beam,or equivalent light beam, of a conventional end-point detection system(not shown) associated with a CMP apparatus, which window is preferablyrectangular in shape, the pad 10 is placed in a fixture, or mold,consisting of two flat plates 14, 15 that may be heated, or may not beheated, as shown in FIG. 2. The plates 14, 15 may cover the entire pad10, or cover only the local area 12. Polymer 13, which is either heatedto a temperature that causes a flowing state thereof, or is treatedexothermically to cause such flowing state in a well-known manner, isinjected through an injection gate 16, while the atmosphere in theformed cavity is removed through a vent 17. Once the cavity iscompletely filled with the polymer, the polymer is cooled at acontrolled rate in order to prevent excessive shrinkage of the window,and in order to maintain the clarity of the polymer. Once the pad hasbeen removed from the mold-fixture, further treatment of the window, ifrequired, may be performed in order to remove any irregularities formedvia the injection gate 16 and vent 17. The mold-fixture preferablyremoves any irregularities during the injection process by closing thegate and vent holes at a specific time, thereby making the polymerplanar with the cavity. Vent 17 may not be required for a more porouspad, where the atmosphere in the cavity is able to evacuate through thematerial of the polishing pad itself. The polymer may be amorphous,semi-crystalline, crystalline or elastomeric material. Laser-transparentpolymers that may be used, but not limited to, are clear: Polypropylene(PP), acrylonitrile-butadiene-styrene (ABS), polycarbonate (PC),acrylic-styrene-acrylonitrile (ASA), polyphenylene ether (PPE), andpolyetherimide (PEI).

[0022] The integrity of the window of the polishing pad is formed bydiffusion of the flowing polymer into the porous pad. FIGS. 3A and 3Bshow the completed polishing pad-assembly, and the diffusion zone at thepad-material/window interface. The depth of the diffusion “d” isdependent on the temperature of the pad matrix during the injectionprocess, the porous nature of the pad, and the viscosity of the polymeror polymers used. In the case where the polymer is heated, the diffusiondepth “d” is greater when the matrix of the pad at the interface is heldat or above the melting point or above the softening point of thepolymer. Also, the depth is also function of the interconnecting natureof the pad matrix, the pore size thereof, and the molecular weight ofthe polymer. Modifying the density of the pad-material around the windowalso controls the penetration of the polymer into the pad-matrix. Bycreating a lower density zone around the window, the diffusion isincreased. By creating a higher density zone around the window, thediffusion zone is decreased, and may be eliminated at a high-densitybarrier. Further structural integrity may be achieved by attaching anadhesive layer, other impervious layer, or both, to the back, or rear,of the window and pad-matrix, in a manner similar to that describedhereinbelow with respect to the embodiment of FIG. 6. These layers maybe polymer adhesive films, or other films, that are attached to the backside of the pad with heat, or applied in an uncured liquid state andallowed to cure. In either case, the additional layer or layers ofsufficient clarity and transparency to allow for the proper functioningof CMP end-point detection. In some cases, an area in the adhesive layeror impervious layer may be completely removed that is slightly smallerthan the area of the transparent region in the pad, in order to ensuresuch laser-transparency. In such a case, the adhesive layer orimpervious layer forms a circumferential shoulder about the bottomperimeter of the transparent region, allowing for increased integrity ofthe window, in a manner depicted in FIG. 6, and described hereinbelow.The adhesive layer may be used to secure or affix the pad to a platen ofa CMP apparatus in a well-known manner.

[0023] According to the invention, the window formed in the polishingpad preferably has an approximate opacity range of 0-70% (30-100%transmission) for a laser of a wavelength in the range 150-3500 nm. Mostlaser systems for end-point detection are approximately in the range of600-700 nm.

[0024] Referring to FIG. 4, there is shown a modification of thepolishing pad with window of the invention, which window is stepped. Thelocal region or area 13 for the window is formed with a shoulder, orlarger-diameter, circumferential cutout section 18 on the non-workingside thereof. As before, the cavity is injected with flowing polymer, bywhich a stepped window is formed with a larger cross-sectional area 18′adjacent the rear, non-working surface of the polishing pad. The majoradvantage with this modification is the increased integrity of thewindow. In particular, since the enlarged section 18′ of the windowsection 18 at the base of the window is supported by the platen 19during operation in a chemical-mechanical planarization apparatus, thereis decreased tendency for the polymer forming the window to be ejectedor to fall out during polishing. This modification is more advantageousfor pad and/or window materials where an acceptable diffusion zonecannot be obtained. If necessary, a reinforcing adhesive layer, or otherimpervious layer, to the back, or rear, of the window and pad-matrixmay, also, be provided, as explained above.

[0025] Referring to FIG. 5, there is shown a second embodiment. In thisembodiment, the local section or area of the polishing pad is notinitially voided or cut out, but rather the pad-material at the localsection 13 is of lower or decreased density than that the rest of thepad-material matrix. When the flowing polymer is injected into the localarea, the voids in the lower-density material thereat are filled withthe polymer, thereby providing a section sufficiently transparent to theend point laser. In this embodiment, the pad-material forming thelow-density area is preferably the same material as the rest of theporous pad itself. However, the density thereof is lower, such as, forexample, less than 1 g/cm{circumflex over ( )}3. It is, of course, to beunderstood that the above-described specifications are not limiting,with the present invention encompassing a large range, as would beevident to one of ordinary skill in the art. For example, the density ofthe window-region may vary depending on the material and polymer used,opaqueness, laser-frequency used, and the like.

[0026] Referring to FIG. 6, there is shown a third embodiment of theinvention. In this embodiment, a distinct and separate transparentwindow-plug 22 is molded separately independently of the pad 20, andinserted into the cutout or opening of the pad. An impervious layer 24,which is preferably a polymer adhesive film, or other film, is attachedto the back side or rear of the pad with heat, or applied in an uncuredliquid state and allowed to cure. The impervious layer 24 is preferablya polyurethane adhesive film which is aligned with thepreviously-inserted window-plug 22, and which has a rectangular openingsection 22′ that is smaller in cross section than the window-plug 22proper, in order to provide an overlapping section with respect to thewindow-plug 22. Heat and pressure are then applied, whereupon thepolyurethane-film flows into the pad itself, and also bonds with thewindow-plug 22 via the overlapping section thereat, as seen in FIG. 6.After the polymeric film has cured or cooled, a sealed boundary iscreated around a juxtapositioned portion of the transparent window-plug,as clearly shown in FIG. 6. A bottom adhesive layer 32 for securing thepad to a platen is then applied to the pad, and a small rectangularopening is also formed for alignment with the opening 22′ of theimpervious layer 24. The impervious layer 24 prevents infiltration into,and contamination of, the adhesive layer 32 by CMP slurry and otherCMP-process chemicals during the CMP process. This prevents adhesivedegradation and potential failure of the bond between the pad andplaten. The impervious layer 24 is an adhesive film about 3 mil. thick,having a shore A hardness of 86, flowing at about 200 degrees F., and isheated to 300 degrees F. during the above-described process.

[0027] While the above-description has been given with regard to theformation of a window in a porous pad, and in particular to the porouspaper-making-fiber-matrix polishing pads disclosed U.S. patentapplication Ser. Nos. 10/087,223 and 10/349,201, other types of porouspads or non-porous pads may also be provided with the window of thepresent invention. Formation of the window of the invention in anonporous pad is similar to first embodiment described above for aporous pad, where there is created a higher-density zone around theopening in the nonporous pad for the window, the diffusion zone thusbeing decreased or eliminated altogether at a high-density barrier, asdescribed above. Further structural integrity may be achieved byattaching an adhesive layer, or other impervious layer, to the back ofthe window or nonporous pad, as described above. In this case, theadditional layer must be of sufficient clarity to allow properfunctioning of the end-point detection.

[0028] While specific embodiments of the invention have been shown anddescribed, it is to be understood that numerous changes andmodifications may be made therein without departing from the scope andspirit of the invention as set forth in the appended claims.

What is claimed is:
 1. A polishing pad for use in chemical mechanicalpolishing of substrates, said polishing pad having a polishing surface,comprising: a porous fibrous matrix comprising paper-making fiber; abinder for binding said fibers; said fibrous matrix forming a porousstructure by which polishing slurry and polishing debris during chemicalmechanical polishing of substrates are temporarily stored for subsequentrinsing away, and for enhanced flow-distribution of the polishingslurry; said fibrous matrix comprising an end-point-detectiontransparent window section for allowing light beams from an end-pointdetection apparatus to pass therethrough.
 2. The polishing pad for usein chemical mechanical polishing of substrates according to claim 1,wherein said fibrous matrix comprises a lower-density area, saidlower-density area having a density less than at least part of theremainder of said fibrous matrix; said end-point-detection transparentwindow section comprising said lower-density area and laser-transparentpolymer material interspersed in said lower-density area.
 3. Thepolishing pad for use in chemical mechanical polishing of substratesaccording claim 2, wherein said at least part of the remainder of saidfibrous matrix comprises a higher-density surrounding sectionimmediately adjacent to, and encompassing, said lower-density area; saidhigher-density, surrounding section controlling the degree of dispersionof said laser-transparent polymer material interspersed in saidlower-density area into the remainder of said fibrous matrix exterior ofsaid lower-density area.
 4. The polishing pad for use in chemicalmechanical polishing of substrates according claim 1, wherein saidend-point-detection transparent window section compriseslaser-transparent polymer material; said fibrous matrix comprising asurrounding section that immediately surrounds said end-point-detectiontransparent window section; said surrounding section comprising adiffusion zone; said laser-transparent polymer material being diffusedin said diffusion zone of said surrounding section, whereby saidwindow-section is bonded to said fibrous matrix.
 5. The polishing padfor use in chemical mechanical polishing of substrates according claim4, wherein said fibrous matrix comprises a front working surface for usein polishing and a back surface for mounting to a platen of a CMPapparatus; said end-point-detection transparent window section beingmade of laser-transparent polymer material; said end-point-detectiontransparent window section being stepped and having a largercross-sectional area toward said back surface for increasing structuralintegrity.
 6. The polishing pad for use in chemical mechanical polishingof substrates according claim 4, wherein said fibrous matrix comprises afront working surface for use in polishing and a back surface formounting to a platen of a CMP apparatus; said polishing pad furthercomprising a reinforcing impervious layer attached to said back surfacefor providing additional structural integrity to said window section insaid fibrous matrix; said reinforcing impervious layer having a cutoutin alignment with said end-point-detection transparent window sectionfor allowing the light beam from an end-point-detection device to passtherethrough, said reinforcing impervious layer being fused to said backsurface.
 7. The polishing pad for use in chemical mechanical polishingof substrates according claim 6, wherein reinforcing impervious layer isfused to said back surface by heating said reinforcing impervious layerto cause a fused bond with said back surface; said polishing pad furthercomprising an adhesive backing layer for attaching said fibrous matrixto a platen; said adhesive backing layer being attached to saidreinforcing impervious layer; said reinforcing impervious layer beingsandwiched between said window section and said adhesive backing layer;said reinforcing impervious layer preventing slurry from contacting saidadhesive backing layer during the CMP polishing process; said adhesivebacking layer also having a cutout in alignment with said cutout of saidreinforcing impervious layer for allowing the light beam from anend-point-detection device to pass therethrough.
 8. The polishing padfor use in chemical mechanical polishing of substrates according claim1, wherein said end-point-detection transparent window section comprisesa window-plug made of laser-transparent polymer material; said fibrousmatrix having a cutout section in which said window-plug is received;said fibrous matrix comprising a front working surface for use inpolishing and a back surface for mounting to a platen of a CMPapparatus; said polishing pad further comprising a reinforcingimpervious layer attached to said back surface for providing structuralintegrity to said window-plug in said fibrous matrix; said reinforcingimpervious layer having a cutout in alignment with said cutout sectionof said fibrous matrix for allowing the light beam from anend-point-detection device to pass therethrough; said cutout being ofless cross-sectional area than the juxtapositioned portion of saidwindow-plug thereat in order to form an overlapping section of saidreinforcing impervious layer that overlaps said juxtapositioned portionof said window-plug; said overlapping section of said reinforcingimpervious layer being fused to said juxtapositioned portion of saidwindow-plug for bonding said reinforcing impervious layer to saidjuxtapositioned portion of said window-plug; said reinforcing imperviouslayer also being fused to said back surface of said fibrous matrix. 9.The polishing pad for use in chemical mechanical polishing of substratesaccording claim 8, wherein said polishing pad further comprises anadhesive backing layer for attaching said fibrous matrix to a platen;said adhesive backing layer being attached to said reinforcingimpervious layer; said reinforcing impervious layer being sandwichedbetween said window-plug and said adhesive backing layer; saidreinforcing impervious layer preventing slurry from contacting saidadhesive backing layer during the CMP polishing process; said adhesivebacking layer also having a cutout in alignment with said cutout of saidreinforcing impervious layer for allowing the light beam from anend-point-detection device to pass therethrough.
 10. A method of formingan end-point-detection window in a polishing pad for use in chemicalmechanical polishing of substrates, said polishing pad having apolishing surface and comprising a porous fibrous matrix made ofpaper-making fibers, and a binder for binding said paper-making fibers;said fibrous matrix having a working polishing surface and a back,non-working surface, said method comprising: forming an area throughsaid fibrous matrix from said working polishing surface to said back,non-working surface; said step of forming comprising creating in saidfibrous matrix a region that is transparent to light beams emanatingfrom a CMP end-point detection device; and filling said region of saidstep of creating with material that is transparent to light beamsemanating from a CMP end-point detection device.
 11. The method offorming an end-point-detection window in a polishing pad for use inchemical mechanical polishing of substrates according to claim 10,wherein said step of creating a region comprises creating an opencutout; said step of filling comprising filling said open cutout withsaid material that is transparent to light beams emanating from a CMPend-point detection device; said step of filling comprising causing saidmaterial that is transparent to light beams emanating from a CMPend-point detection device to a achieve a flowing state thereof, anddirecting the flowing material to said open cutout.
 12. The method offorming an end-point-detection window in a polishing pad for use inchemical mechanical polishing of substrates according to claim 11,wherein said step of filling comprises inserting said fibrous matrix ina mold having an inlet; said step of directing comprising injecting saidflowing material to said inlet and into said mold for filling said opencutout with said flowing material; said step of filling also comprisingbinding said material to said fibrous matrix at surrounding portions ofsaid fibrous matrix; said step of binding comprising diffusing saidflowing material into said surrounding portions of said fibrous matrix.13. The method of forming an end-point-detection window in a polishingpad for use in chemical mechanical polishing of substrates according toclaim 12, wherein said step of creating an open cutout in said fibrousmatrix comprises creating a stepped region defining a largercross-sectional section at said back, non-working surface; said step offilling causing a stepped end-point-detection window to be formed insaid open cutout comprising a larger cross-sectional shoulder adjacentsaid back, non-working surface which overlaps adjacent juxtapositionedsections of said fibrous matrix; said step of binding further comprisingdiffusing said material to said fibrous matrix at the overlappedsections of said fibrous matrix.
 14. The method of forming anend-point-detection window in a polishing pad for use in chemicalmechanical polishing of substrates according to claim 10, wherein saidstep of creating a region comprises creating an open cutout; said stepof filling comprising inserting in said open cutout a separate andindependent integral window-plug made of said material that istransparent to light beams emanating from a CMP end-point detectiondevice; binding said integral window plug in said open cutout; said stepof binding comprising forming a binding film layer to said back,non-working surface of said fibrous matrix; said step of binding causingthe material of at least a portion of said binding film layer to bondwith respective, juxtapositioned portions of said back, non-workingsurface of said fibrous matrix and said window-plug.
 15. The method offorming an end-point-detection window in a polishing pad for use inchemical mechanical polishing of substrates according to claim 14,wherein said step of binding comprises heating a binding film layer;said step of heating raising the temperature of at least a portion ofsaid binding film layer to a temperature that causes at least partialflow of the material of said at least a portion of said binding filmlayer.
 16. The method of forming an end-point-detection window in apolishing pad for use in chemical mechanical polishing of substratesaccording to claim 14, further comprising: forming an opening in abinding film layer in alignment with said open cutout of said fibrousmatrix so that light beams emanating from a CMP end-point detectiondevice may pass transparently therethrough; said step of forming anopening comprising making an opening that is of a smaller cross sectionthan the cross section of said open cutout of said fibrous matrix; saidstep of making an opening comprising creating overlapping portions of abinding film layer with respect to juxtapositioned adjacent sections ofsaid window-plug, said overlapping portions being at least part of saidat least a portion of said binding film layer of said step of heating.17. The method of forming an end-point-detection window in a polishingpad for use in chemical mechanical polishing of substrates according toclaim 16, further comprising: attaching a CMP-platen-attaching adhesivelayer to said binding film layer; and making an opening in saidCMP-platen-attaching adhesive layer in at least approximate alignmentwith said opening of said binding film layer.
 18. The method of formingan end-point-detection window in a polishing pad for use in chemicalmechanical polishing of substrates according to claim 10, wherein saidstep of creating in said fibrous matrix a region that is transparent tolight beams emanating from a CMP end-point detection device comprisesmaking a less dense region in said fibrous matrix.
 19. The method offorming an end-point-detection window in a polishing pad- for use inchemical mechanical polishing of substrates according to claim 10,wherein said step of filling comprises causing said material that istransparent to light beams emanating from a CMP end-point detectiondevice to a achieve at least partial flow thereof, and directing theflowing material to said open cutout; said step of filling alsocomprising binding said material to said fibrous matrix at surroundingportions of said fibrous matrix; said step of binding comprisingdiffusing said flowing material into said surrounding portions of saidfibrous matrix.
 20. The method of forming an end-point-detection windowin a polishing pad for use in chemical mechanical polishing ofsubstrates according to claim 19, wherein said step of filling furthercomprises allowing said material to cool; said step of creating an opencutout in said fibrous matrix comprises creating a stepped regiondefining a larger cross-sectional section at said back, non-workingsurface; said step of filling causing a stepped end-point-detectionwindow to be formed in said open cutout comprising a largercross-sectional shoulder adjacent said back, non-working surface whichoverlaps adjacent juxtapositioned sections of said fibrous matrix; saidstep of binding further comprising diffusing said material to saidfibrous matrix at the overlapped sections of said fibrous matrix.
 21. Amethod of forming an end-point-detection window in a polishing pad foruse in chemical mechanical polishing of substrates, said polishing padhaving a polishing surface and comprising a porous fibrous matrix; saidporous fibrous matrix having a working polishing surface and a back,non-working surface, said method comprising: (a) forming an area throughsaid fibrous matrix from said working polishing surface to said back,non-working surface; (b) said step (a) comprising creating in saidfibrous matrix a region that is transparent to light beams emanatingfrom a CMP end-point detection device; (c) filling said region of saidstep of creating with flowing material that is transparent to lightbeams emanating from a CMP end-point detection device to provide saidend-point-detection window; (d) binding said end-point-detection windowto portions of said porous fibrous matrix surrounding said region; (e)said step (d) comprising diffusing flowing material into saidsurrounding portions of said porous fibrous matrix and into saidend-point-detection window.
 22. The method of forming anend-point-detection window in a polishing pad for use in chemicalmechanical polishing of substrates according to claim 21, wherein saidstep (e) comprises diffusing said flowing material of said step (c) intosaid porous fibrous matrix at adjacent, juxtapositioned portions of saidporous fibrous matrix surrounding said region.
 23. The method of formingan end-point-detection window in a polishing pad for use in chemicalmechanical polishing of substrates according to claim 21, wherein saidstep (e) comprises diffusing fusing material into said back, non-workingsurface of said porous fibrous matrix and into the back section of saidend-point-detection window adjacent said back, nonworking surface ofsaid porous fibrous matrix.